What if Republican governor Brian Kemp of Georgia wanted his state’s electoral votes to go towards Donald J. Trump (R-New York) even though Joe Biden (D-Delaware) won most of the votes? This is a possibility that the Supreme Court is now entertaining.
The Georgia legislature could vote to allow the Governor to appoint electors, but in that case, there would be no need for an election at all. There'd be no popular vote to ignore. OTOH, I don't see such a delegation happening. Recall that in 2020 many Republican legislators rejected out of hand the suggestion that they use their prerogatives via control of the state legislature to negate the popular vote in the state.
I would analyze the current Court's rulings in light of the Justices' records before there was a Donald Trump. Their driving philosophical position is that Americans should do politics first and come to the courts only when politics fails. Dobbs says that abortion is a political issue, an argument very hard to refute considering how everyone has politicked about it for fifty years. The same is true of the appointment of electors.
The state legislature determines how electors will be chosen. The state legislatures in all but two states have chosen to allocate all of the state's electors by statewide popular vote. Maine and Nebraska use a different method. Constitutionally, the Maine and Nebraska cases make clear that the legislature can do anything it wants, within the guaranty of a "republican form of government," whatever that means.
By what principle is SCOTUS supposed to rule that Maine is OK but Gubernatorial appointment is not? The governor was elected by popular statewide vote, right? To say that a governor elected by statewide vote cannot be delegated the authority to do what would otherwise be done by a separate statewide vote strikes me as a big leap constitutionally.
That's not to say it isn't a big leap politically, and I doubt any state legislature would ever pass such a law. Which is why speculation about what could be done under the Independent State Legislature doctrine needs to consider what would actually be done under it. If, as in Dobbs, SCOTUS says that the people of the state need to do politics about how the state chooses electors, that may further encourage otherwise apathetic voters to pay attention to what goes on in the state capital. That's not clearly a bad thing.